In some applications it is necessary to compose a security code to give access for an authorised person to an apparatus such as a personal computer workstation, or a protected location such as a strong room, or a specific location of a building or the person's own home. For this, it has already been proposed in the document GB 2 129 176 to provide a user with a wrist watch, in which a security code has been stored in a non-volatile memory. The back-cover of the watch case contains electric contacts for contact with the wrist of a user. The watch also contains means for transmitting the security code. When a finger of the wearer of the personal watch comes into contact with a conductive surface of a receiver of a location to be accessed, the security code is automatically transmitted numerically via resistor. The signals of the security code are therefore transmitted through the hand of the wearer of the watch from a processing unit of the watch to the receiver. This security code is therefore dependent on the physical parameters of the wearer of the watch and this can enable identification of the authorised person to enter the protected location.
A disadvantage of such an access procedure is that the transmission of this security code is also dependent on the capacitor value defined between the wrist of the user of the watch and earth. As a result, the type of shoes worn by the user of the watch can have a considerable influence on recognition of the security code transmitted to the receiver of the location to be accessed.
Other solutions are conceivable for input of the security code. In more complicated devices, a check can be conducted via voice recognition, a fingerprint or the internal structure of the eye to provide a security code for access to an apparatus or a given location.
More simply, the security code can be entered on a watch and transmitted in particular by means for transmitting radio-frequency, optical or acoustic signals. This security code can be input by different buttons or keys of the watch. According to the present invention, the security code is input, for example, by a user by means of a finger or a stylus on a touch screen of an electronic device.
In the field of character recognition, it is known to use a touch screen fitted with several touch-sensitive pads. The document U.S. Pat. No. 4,139,837, which describes a wrist watch with such a touch screen, may be cited in this regard. In this document, the sensitive pads of the touch screen are linked to a logic circuit and to a processing unit for the recognition of characters such as digits or arithmetic operators indicated by the finger of a user. The processing unit recognises the digit or operator indicated by the finger of the user taking into account the start sensitive pad, the last sensitive pad of the finger and sensitive pads touched during movement of the finger. Thus, with the aid of this touch screen it is possible to achieve recognition of a character by movement of the finger on the sensitive pads of the glass. This watch can be used as a calculator, for example. However, there is no provision in this watch for entering a security code to allow access to a particular function of the watch, an apparatus or location remote from the wearer of the watch.
Therefore, the subject of the invention is a method of input of a security code by means of a touch screen of an electronic device for access to a function, apparatus or location, which overcomes the disadvantages of the prior art and which allows said security code to be entered quickly and easily.